Shorter Duration Of Tonic Immobility Research Articles

Investment Trade-Off between Mating Behavior and Tonic Immobility in the Sweetpotato Weevil Cylas formicarius (Coleoptera: Brentidae).

Numerous studies have confirmed that the trade-off between anti-predator behavior and mating behavior occurs in certain insect species. This suggests that insects invest more in anti-predator behavior, and fewer resources or time can be used in mating behavior. However, few studies focus on tonic immobility, an important anti-predator behavior in nature, and different stages in mating behavior. Tonic immobility (TI) is considered to be an important anti-predator behavior. Herein, we investigated the relationship between TI and mating behavior in the sweetpotato weevil (SPW), Cylas formicarius. As the first step, we artificially selected SPWs for the longer duration of TI (L-strain) and the shorter duration of TI (S-strain). The effect of courtship and copulation on the duration of TI in two artificial selection strains was tested. Furthermore, we compared the frequency and duration of two mating behaviors in four kinds of pairs (LF×LM, LF×SM, SF×LM, and SF×SM: LM-L-strain male; SM-S-strain male; LF-L-strain female; SF-S-strain female). Finally, we tested insemination success in four kinds of pairs (male and female SPWs from the L-strain or the S-strain). The courtship and copulation significantly reduced the duration of TI. Pairs with males from the L-strain showed lower frequency and longer duration of courtship than pairs with males from the S-strain. Similarly, males from L-strain pairs showed a longer period of copulation than pairs with males from the S-strain. However, there is no significant difference in the frequency of copulation and the success of insemination. These results support that there was a significant trade-off between TI and courtship as well as copulation in the SPW.

Defensive responses in invertebrates: Evolutionary and neural aspects.

Lower invertebrates exhibit both morphological and behavioral defensive responses to aversive stimuli, characterized by withdrawal. Typical immobility responses are "sinking" in Rotifers and "crumpling" in Cnidaria. They also display individual adaptation and phenotypic plasticity but not tonic immobility (TI). The higher phyla with a more organized nervous system have developed morphological and behavioral defensive strategies including TI, occurring both in natural and laboratory conditions. There are general but also specific prey-predator mechanisms, that have coevolved leading to reciprocal phenotypic plasticity. The evolution of traits differentiated in subpopulations has been described in many species (animal personality). In insects the variability in TI is heritable and inversely related to boldness. In two genetic lines of beetles with long and short TI duration, the long duration line has higher survival rate but lower mating success (behavioral syndromes). TI may have an adaptive significance also in intraspecific interactions in the context of sexual selection.

Trade-off Investment between Tonic Immobility and Mate Search in the Sweetpotato Weevil, Cylas formicarius (Coleoptera: Brentidae).

Simple SummaryTonic immobility (TI) is considered as an important anti-predator strategy. In order to know the relationship between TI and mating behavior, we investigated the cost–benefit between TI and mate search in the sweetpotato weevil (SPW), Cylas formicarius. In this study, we used Y-tube olfactometer and determined that male mate searching increase after 3 h at night. Then, we confirmed that TI was affected by mate search in the males. Because the duration of TI of the male during mate search was significantly shorter duration than the males from the control. However, TI does not affect mate search in the females. Finally, the Y-tube olfactometer was used to compare the duration of mate search and the proportion of orientation towards the females in two artificial selection groups of the male SPWs. In this experiment, we found that mate search was affected by TI. Our study results provided a clear evidence that there is a trade-off between mate search and TI behavior in males of the SPW. Further, we quantified investment of anti-predator behavior and mating behavior by measuring the duration of TI and mate search in the SPW. We believe, these methods can be useful to determine the cost–benefit between anti-predator behaviors in the prey(s) and predator(s) in other species too.Tonic immobility (TI) is a well-known anti-predator strategy adopted by diverse preys. Numerous studies on the cost–benefit involve in TI have been reported. Although, some studies have reported the effect of mating behavior on TI, few studies highlight the phases of mate search. In the present study, we investigated the relationship between mate search and TI behavior in the sweetpotato weevil (SPW), Cylas formicarius (Coleoptera: Brentidae). First, we found the most active mate search period of male SPW within 24 h. Then, we measured whether the duration of TI of virgin male and female were affected during the mate search. In the end, the Y-tube olfactometer was used to compare the duration of mate search and the proportion of orientation towards the females in two artificial selection groups of the male SPW with longer and shorter duration of TI. Our study confirmed that male mate searching increase after 3 h at night, and up to 73% at midnight, TI was affected by mate search in male, because the duration of TI of the male during mate search (Mean ± SE = 214.53 ± 22.74 s) was significantly shorter duration than the control (679.64 ± 69.77 s). However, mate search did not affect the strength of TI in the females tested. This study determined that mate search was affected by TI due to males from the group with shorter duration of TI who had 28% higher proportion of orientation towards the females than the males with longer duration of TI. Investment trade-off between TI and mate search was confirmed in the males of the SPW.

Lines selected for different durations of tonic immobility have different leg lengths in the red flour beetle Tribolium castaneum

Abstract Tonic immobility is an adaptive anti-predator behaviour observed in many species. This anti-predator behaviour is often correlated with a species’ movement motivation, so a relationship between the duration of tonic immobility and morphological traits supporting movement would be expected. Using the red flour beetle, Tribolium castaneum, we carried out two-way artificial selection for the duration of tonic immobility over more than 43 generations, establishing populations with longer (L) and shorter (S) tonic immobility durations compared to those of a non-selected control (C) population. Here, we investigated differences in walking motivation and leg length between the selected populations. Walking motivation was significantly higher in beetles from the S population than that in those from the L population. Moreover, S-population beetles of both sexes had significantly longer legs than those from L and C populations. The present results suggest the evolution of longer legs in response to selection pressure for a shorter duration of tonic immobility in T. castaneum.

Are there facial indicators of positive emotions in birds? A first exploration in Japanese quail

The positive aspect of emotions, like pleasure, remains overlooked in birds. Our aim was to contribute to the exploration of facial indicators of positive emotions. To observe contrasting emotional expressions, we used two lines of Japanese quail divergently selected on their inherent fearfulness: a fearful line (long tonic immobility duration: LTI) and a less fearful line (short tonic immobility duration: STI). To induce positive emotions, we gave individual quail the opportunity to perform a rewarding behaviour, dustbathing, in an unfamiliar cage. More STI than LTI quail expressed dustbathing and latencies to dustbathe were significantly shorter in STI than LTI quail. This result indicated that the lines of quail differed in their fearfulness of the situation. We observed crown feather height, throat feather angle and pupil surface before (control) and during dustbathing. We found significant increases in crown feather height, pupil area and angle of throat feathers between the control and the dustbathing phases in STI quail, and pupil area correlated positively with crown feather height. In LTI quail, the angle of throat feathers increased during dustbathing, but the other parameters did not differ. We argue that variation in crown feather height and pupil area may provide indications of positive emotions in Japanese quail.

Effects of environmental complexity on fearfulness and learning ability in fast growing broiler chickens

Increasing environmental complexity, i.e. by providing environmental enrichment, has been suggested as a way to improve broiler chicken welfare. One issue affecting broiler welfare is the level of fearfulness of the flock. Exaggerated fear responses may cause smothering and mortality. Environmental complexity has been found to reduce fearfulness in several species. It is known to promote the development of cognitive functions, including learning and memory. The aim of this study was to test the hypothesis that housing environments of different complexity, due to environmental enrichment or manipulation of standard resources, have an effect on learning ability and fearfulness in broilers. Fifty-eight pens with approximately 500 broilers in each (Ross 308), corresponding to a stocking density of 40 kg/m2, were used. Commercial feed and water were provided ad libitum, and wood shavings were used as litter material. Five environmental enrichment treatments (roughage, vertical panels, straw bales, elevated platforms at different heights), three treatments where the standard resources had been manipulated (increased distances between feed and water, lower stocking density) and one control group were randomly assigned to each pen. At 21 d, 10 broilers from each pen with treatments straw bales, elevated platforms, lower stocking density and control group were tested in a passive avoidance-learning task. At 31 d, 30 broilers from each pen from all treatment groups were subjected to a tonic immobility test. There was a tendency for broilers housed with access to straw bales to have better performance in a passive avoidance-learning task compared to broilers in the control group (F3,92 = 2.22; P = 0.091). In addition, chicks housed with access to 30 cm elevated platforms displayed shorter duration of tonic immobility compared to chicks housed with increased distance between feed and water (F8,49 = 2.22; P = 0.041; Tukey’s test P = 0.038), suggesting decreased fearfulness. The results show that increasing environmental complexity can have positive effects on decreasing fearfulness and promoting learning ability in broiler chickens, improving their welfare.

Effects of a 16-hour light, 8-hour dark lighting schedule on behavioral traits and performance in male broiler chickens

SUMMARY The objective of this study was to examine the effects of a 16L:8D lighting schedule from d 2 of age through a 6-wk production trial on the performance and behavior of Cobb broiler males compared with a continuous 24-h light schedule (control). Behavioral tests included social reinstatement behavior measured in runway tests and fear response measured by tonic immobility. The 16L:8D group had BW and FCR similar to control birds at 6 wk. Based on behavior observations by scan sampling at 0900 to 1100 h and 1400 to 1600 h, the number of chicks eating, drinking, walking-standing, and pecking increased under the 16L:8D lighting schedule, whereas resting (sitting and sleeping) decreased (P ≤ 0.05). The 16L:8D group also exhibited comfort behaviors, such as preening and wing-shaking, more extensively than did control birds (P ≤ 0.05). Broilers in the 16L:8D group had a shorter duration of tonic immobility (P ≤ 0.05) at 11 and 35 d of age, which might represent less fearfulness. In runway tests at 13 and 30 d of age, the 16L:8D group exhibited shorter latencies to reach the zone of stimulus birds and spent more time near the stimulus birds (P ≤ 0.05). We therefore suggest that the birds in the 16L:8D group had a greater degree of sociality. Although we did not measure whole-day activity, we speculate that this greater sociality might have resulted from increased interactions among birds caused by increased activity during the observation periods. The16L:8D program tended to have more natural daytime behavioral patterns in broilers, to reduce fearfulness (and thus psychological stress), and to increase sociality. We conclude, based on the morning and afternoon measurements of this study, that birds in the 16L:8D group had a better welfare status than control birds without affecting 42-d broiler performance of the strain used.

Biogenic amines, caffeine and tonic immobility in Tribolium castaneum

Biogenic amines are physiologically neuroactive substances that affect behavioural and physiological traits in invertebrates. In the present study, the effects of dopamine, octopamine, tyramine and serotonin on tonic immobility, or death-feigning, were investigated in Tribolium castaneum. These amines were injected into the abdomens of beetles artificially selected for long or short duration of tonic immobility. In beetles of the long strains, the durations of tonic immobility were shortened by injection of dopamine, octopamine and tyramine, and the effects of these amines were dose-dependent. On the other hand, serotonin injection did not affect the duration of tonic immobility. In the short-strain beetles that rarely feign death, no significant effects of the amines were found on the duration of tonic immobility. Brain expression levels of octopamine, tyramine and serotonin did not differ between long- and short-strain beetles, in contrast to the higher dopamine levels in short strains previously reported. Caffeine decreased the duration of death-feigning in both oral absorption and injection experiments. It is known that caffeine activates dopamine. Therefore, the present results suggest that the duration of tonic immobility is affected by dopamine via the dopamine receptor in T. castaneum.

Divergent selection for inherent fearfulness leads to divergent yolk steroid levels in quail

AbstractAvian yolk steroid levels may vary according to maternal condition or environmental factors, causing epigenetic modulation of offspring phenotype. Here we test whether artificial selection based on divergent duration of tonic immobility (TI) in Japanese quail (i.e., divergent inherent fearfulness) is correlated with divergent levels of yolk steroids. We analysed yolk steroid levels and egg quality in quail selected for either long or short duration of TI. Yolk steroids, i.e., immunoreactive progesterone and androstenedione, were found to be significantly less concentrated in eggs of the high inherent fearfulness line compared to eggs of the low inherent fearfulness line. A similar trend was found with testosterone levels. Larger eggs with lighter eggshell were also found in more fearful quail. Hence, the selection for divergent fearfulness has led to correlated changes in yolk steroid levels and egg quality. These data suggest that hormones of maternal origin, egg quality and genetic background may all contribute to line differences in phenotype. A modulation of progesterone concentrations by selection for behaviour in egg yolk is reported here for the first time. Although the effect of this hormone on avian embryos remains unknown, we argue it may have significant effects on phenotypic outcome.

Behavioural and endocrine fear responses in Japanese quail upon presentation of a novel object in the home cage

Most tests used to study fear in birds involve transferring them to a novel environment, which constitutes a bias in studies aiming at identifying the neural correlates of a specific fear-inducing situation. In order to investigate fear in birds with minimum interference by humans, behavioural and endocrine responses to the presentation of a novel object in the home cage were investigated in two lines of Japanese quail divergently selected for long or short duration of tonic immobility, a behavioural index of fear. Presentation of the novel object induced typical fear responses (avoidance of the object, increased pacing and increased plasma corticosterone levels) that were similar in the two lines of quail. Presentation of a novel object in the home cage thus appears to be a suitable stimulus to induce fear reactions in quail, with minimum interference from other motivational systems. The fact that quail of both lines reacted similarly in this test, while they are known to differ greatly in their behavioural responses to other fear-inducing tests, illustrates the multidimensional nature of fear.

Relationship between hypothalamic-pituitary-adrenal axis responsiveness and age, sexual maturity status, and sex in Japanese quail selected for long or short duration of tonic immobility

The influences of age (4 to 12 wk), sexual maturity status, and sex on hypothalamic-pituitary-adrenal (HPA) axis responsiveness were investigated by measuring changes in peripheral basal levels of corticosterone (B) and responses to 10 min of physical restraint in a crush cage or injection of 1-24 adrenocorticotropic hormone (ACTH) in 2 genotypes of Japanese quail divergently selected for long (LTI) or short (STI) duration of tonic immobility (TI). Although gonad development was more advanced in male STI quail, most birds were still immature at 4 wk of age, but sexual maturity was fully acquired by 6 wk of age in both sexes and genotypes. This change was associated with increases in basal B levels in both genotypes and sexes. On the other hand, HPA axis responsiveness to restraint and adrenal responsiveness to 1-24 ACTH injection remained stable in STI quail, whatever the age. Conversely, significant responses to restraint compared with basal B levels were only observed at 4 and 6 wk of age, and adrenal responsiveness increased with age in LTI quail. Moreover, higher B levels were measured in response to restraint in STI than in LTI quail, whereas similar adrenal responses were measured at 9 and 12 wk of age. We concluded that an increase in basal B levels is associated with the stage of sexual maturity acquired, but it did not affect HPA axis responsiveness or adrenal B response capacity. On the other hand, age affected HPA axis responsiveness and adrenal B response capacity in LTI quail of both sexes but not in STI quail. It is hypothesized that functional HPA axis maturity occurs after 6 wk of age in the LTI genotype, but it is reached by 4 wk of age in the STI genotype. In conclusion, the divergent selection program for TI conducted on quail resulted in changes in HPA responsiveness that probably resulted from differences in development rate and function of the adrenal glands or other upstream structures of the HPA axis.

Influence of mating ratio and group size on indicators of fearfulness and stress of hens and cocks

The effects of the male to female mating ratio on the heterophil to lymphocyte ratio and duration of tonic immobility (indicators of stress and fearfulness, respectively) were analyzed in two different experiments with different group sizes. In Experiment 1, four different mating ratios (1:11, 1:5, 1:3, and 1:1) and 10 different Spanish breeds of chickens were used; each breeding pen had 12 birds. In Experiment 2, two different mating ratios (1:11 and 1:1) and four breeds were analyzed; 60 birds were used. There were significant differences among mating ratios (P < 0.001) for the heterophil to lymphocyte ratio in females of both group sizes. Hens housed with a mating ratio of 1:1 had higher heterophil to lymphocyte ratios than did hens housed with a 1:11 mating ratio in the group with 12 birds (0.53 vs. 0.35) or that with 60 birds (0.76 vs. 0.37). Hens in a mating ratio of 1:1 had significant heterophilia and lymphopenia (P < 0.001). The 1:5 and 1:3 male to female mating ratios did not differ significantly from the 1:11 mating ratio. The effect of the group size was significant when the mating ratio was 1:1 but not when it was 1:11. There was no significant difference among mating ratios in terms of tonic immobility for hens. Cocks housed with a mating ratio of 1:1 and a group size of 60 birds showed shorter duration of tonic immobility (P < 0.05) than did cocks housed with a 1:11 mating ratio (203 vs. 296 s). The results suggest that very high mating ratios should not be used in conservation populations because it increases physiological and psychological stress responses.

Divergent selection for duration of tonic immobility and social reinstatement behavior in Japanese quail (Coturnix coturnix japonica) chicks.

Japanese quail (Coturnix coturnix japonica) were selected over 8 generations for long or short duration of tonic immobility (TI) weighted for independence from social reinstatement (SR) behavior (as measured in a treadmill) and for high or low levels of SR behavior weighted for independence from duration of TI. Divergent selection for long or short duration of TI and for high or low levels of SR behavior resulted in immediate and significant responses that continued throughout the 8 generations. There was no evidence of a plateau in the response to selection in any of the lines. SR responses did not vary in lines selected for duration of TI and vice versa. Selection for short duration of TI led to in an increase in the number of inductions required to induce TI. Selection for low levels of SR behavior led to a decrease in the tendency to move toward conspecifics but not to an increase in the tendency to move away from conspecifics.